______,In a small bowl, sprinkle gelatin over cold water; let stand for 1 minute.,Meanwhile, in a small saucepan, combine the sugar, salt and grapefruit juice mixture. Cook and stir until sugar is dissolved. Remove from the heat; stir in gelatin until completely dissolved. Stir in vinegar. Chill until slightly thickened, about 1 hour.,Fold in cucumber and grapefruit sections. Transfer to a 1-qt. mold coated with cooking spray. Refrigerate until firm.,Unmold onto a lettuce-lined serving plate if desired.